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Re: st: Changing range in sts graph

From   "Svend Juul" <[email protected]>
To   <[email protected]>
Subject   Re: st: Changing range in sts graph
Date   Fri, 7 Dec 2007 10:08:49 +0100

Diego Bellavia <[email protected]> wrote:

> I have a Kaplan Meyer curve I built with sts command. 
> The curve is nice but I would like to reduce the range of time showed
> to highlight the first part of the graph (where I have more events).
> I tried with the xscale (range (0 100)) option but without success. 

Maarten suggested:

   sysuse cancer, clear
   stset studytim,failure(died)
   sts graph 
   sts graph if _t < 20

and Allen Buxton suggested:

   local rangelimit=100
   replace _d=0  if _t>`rangelimit'
   replace _t=`rangelimit' if _t>`rangelimit'

Nick got nervous:

Doesn't any messing with _t mess up anything later with the same 
survival dataset? Sounds a bad idea to me. See Maarten's solution. 


Allen's suggestion is right, Maarten's is wrong. It is easy to
see with -sts list- :

   sysuse cancer, clear
   stset studytim,failure(died)
   sts list 

   // Maarten's suggestion:
   sts list if  _t < 20    

   // Allen's suggestion (simplified):
   replace _d=0  if _t>20
   replace _t=min(_t,20)
   sts list

In Maartens suggestion, persons surviving 20 months or more
were excluded from the analysis, leading to a far too pessimistic
survival estimate at 19 months. In Allen's suggestion they
are correctly censored at 20 months.



Svend Juul
Institut for Folkesundhed, Afdeling for Epidemiologi
(Institute of Public Health, Department of Epidemiology)
Vennelyst Boulevard 6
DK-8000  Aarhus C, Denmark
Phone: +45 8942 6090
Home:  +45 8693 7796
Email: [email protected]

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